On the one side stands a courageous former Muslim extremist who abandoned the path of violent jihad to preach tolerance; on the other, a bold and controversial Jewish columnist who has built a reputation as the scourge of the liberal left. Between them they have written two of the most powerful books on radical Islam in Britain.

But this week, a spat between Ed Husain and Melanie Phillips reached a new level of intensity. At the end of last month, Mr Husain used the Guardian’s Comment is Free website to launch an attack on what he sees as a “personal jihad” being waged by Melanie Phillips against critics of Israel — and in this week’s JC, Ms Phillips hits back at Mr Husain, accusing him of being “on the wrong side of the fight to defend civilisation”.

In his Comment is Free invective, Mr Husain accused Ms Phillips, who writes for the Daily Mail, the Spectator and the JC, of “ludicrous, illogical lines of thought” and a “demented mindset”. He said her promotion of the Israeli cause suggested it was more important than others. “The Israel First test, which she seeks to impose on British Muslims (as well as the American President), reeks of racism,” he said.

Until recently, the two writers met regularly to discuss Islamism after Mr Husain renounced violent extremism.

Their relationship was terminally soured, however, by the outbreak of hostilities in Gaza. Mr Husain used his position as head of the anti-extremist Quilliam Foundation to condemn the actions of the Israeli army.

At the time he wrote on Comment is Free: “I’ve spoken out in support of Israel’s right to exist. But Israel’s cold, politically timed killing of more than 300 Palestinians makes me, and millions more rethink our attitude towards Israel.”

The latest exchanges were sparked by a post by Ms Phillips on her Spectator blog in which she questioned the motivation of some of the participants in a recent march against the extremist group al-Muhajiroun on 30 October.

She then responded to the Comment is Free article in kind: “I also wondered — as I had done uneasily right from the start — whether, although he [Ed Husain] had denounced violence, he had never properly renounced Islamic extremism because he could not bring himself to acknowledge its true religious source.”

The row has been further complicated by the intervention of one of the Guardian’s supposedly independent moderators, the anonymous BellaM.

Writing in her official capacity, she said of Ms Phillips: “I imagine she’s like a character in Little Britain who is violently sick every time she hears the words ‘black’ or ‘gay’. Except for Melanie, the word would be ‘Muslim’.” Though she has not been disciplined, the Guardian has reminded BellaM of the paper’s guidelines that staff posting on the site “should uphold a high standard of civility and avoid any behaviour that might bring the Guardian’s good name into disrepute”.

In today’s JC Melanie Phillips writes: “Those who don’t support Israel’s self-defence — such as Ed Husain — are on the wrong side of the fight to defend civilisation. No-one — whether Muslim or Christian, atheist or anything else — can be considered to be a moderate person if he or she is bigoted towards Israel or the Jewish people. You cannot be a moderate bigot.”

But Mr Husain said: “I think Melanie is completely wrong on this issue. There has to be a debate on Israel’s foreign policy and military conduct.”

The polemicist

Melanie PhillipsBorn: June 4, 1951Religion: JudaismKey Works: All Must Have Prizes (1996), an attack on progressive educational philosophy and policy. Londonistan (2006), on UK’s “appeasement” of radical Islam.Journey: Began career writing about social affairs from a left-liberal position on the Guardian. Through her writing on education, society and the family she grew disillusioned with progressive politics. After 9/11, her writing on radical Islam and her championing of Israel has made her the darling of the neo-con right. She is a columnist for the Daily Mail and the Jewish Chronicle, has a Spectator blog and is a regular panellist on The Moral Maze.

The revisionist

Ed HusainBorn: December 25, 1975Religion: IslamKey Work: The Islamist (2007). Husain’s autobiographical account of his radicalisation and subsequent rejection of the ideology of Islamic violenceJourney: As a teenager, Ed Husain was a member of the Young Muslim Organisation and extremist group Hizb-ut-Tahrir, where he became radicalised. After periods studying and working for the British Council in Syria and Saudi Arabia, he rejected what he had been taught by the Islamists. On returning to Britain shortly after the 7/7 bombings, he decided to reject his radical past. In 2008 he founded the Quilliam Foundation to tackle extremism in Britain.